194 Cetacea. MAMMALIA. Cetacea. 
mentary character of the pelvic hones we have already 
spoken, their attenuated form bearing no resemblance 
to the ilia of those quadrupeds in which the posterior 
limbs are present. The ribs are chiefly noticeable in 
respect of their mode of articulation to the dorsal ver- 
tebrae and the great degree of curvature, Avhich is 
necessary to make room for the bulky thoracic viscera; 
a few of the anterior ribs are articulated by their 
heads to the bodies of the vertebrae and by a tubercle 
to the transverse processes, but the remainder have 
only a single mode of connection and have no true 
articular facets at their attached ends. The paddles or 
anterior extremities are worthy of particular considera- 
tion. In them, as has been already hinted, are to be 
found evidences of conformity to type, having a signi- 
flcance not less forcible than that enunciated when 
treating of the bones of the neck. Viewing the limb 
from without, there is nothing to indicate the parts 
severally denominated arm, fore-arm, and shoulders; 
but upon dissection we find all the osseous elements 
ordinarily entering into the constitution of these seg- 
ments fully represented and easily recognized. With 
the exce 2 )tion of the humero-scapulur articulation, all 
the bones are flrmly invested and packed together by 
fibrous tissue, so as to prevent motion upon one 
another; and what is more noticeable, is, that they 
have all become shortened lengthrvise, whilst their 
breadth has somewhat increased, as it were, by com- 
pression within the tightly investing teguments. In 
some species, as in the common mysticete, the digital 
phalanges are more numerous than usually obtains in 
the feet of pentadactyle quadrupeds. If we turn our 
attention to the skeleton of any of the herbivorous 
cetacea — sirch, for example, as that of the Dugong, Plate 
34, fig. 109— not only do we observe a less consider- 
able departure from the ordinary mammalian type, as 
instanced by a comparison of the bones of the hand, 
arm, fore-arm, and shoulder; but in contemjfiating the 
structure of the head and neck, it is evident that we 
have moved a step higher in the scale of organization. 
The seven cervical vertebrae are distinct, though still 
remarkably compressed from before backwards, and 
the skull, whilst visibly contracted in the same direc- 
tion, presents, nevertheless, several peculiarities suffi- 
ciently cogent to demand special notice ; these will be 
immediately considered when describing the general 
characteristics of the Manatidae. Meanwhile we pass 
on to notice very briefly, some of the more striking 
modifications of the viscera, as well as other internal 
and external arrangements equally suggestive. And, 
firstly, as respects the organs of respiration — which are 
chiefly to be noted on account of their singular com- 
munication with the air by means of two nostrils 
situated at the top of the head in the true whales, and 
by a single opening similarly jfiaccd in the dolphins; 
in the herbivorous species these passages terminate in 
front of the muzzle, as in mammalia generally. Hav- 
ing, on several occasions, dissected the common porpoise 
with very great care, we are in a position to testify to 
the accuracy of Baron Cuvier’s account of the singular 
manner in which the windpipe terminates, especially 
within a vertical extension of the phar}Trx, which is 
commonly designated the spouting apparatus, the exter- 
nal openings above being vulgarly called the blow-holes. 
“If we trace the oesophagus upwards,” says Cuvier, 
“ we find that when it arrives opposite the pharynx, it 
appears to divide into two passages, of which one is 
continued onwards to the mouth, while the other 
mounts to the nose; this latter passage being sur- 
rounded with mucous glands and fleshy muscular 
bundles. Some of these are longitudinal, arising from 
the circumference of the posterior orifice of the bony 
nostrils, and descending along that canal to the pharynx, 
and its lateral path. The others are annular and 
appear to be a continuation of the proper muscle of the 
pharynx, and as the larynx rises into this passage in 
the form of an obelisk or pyramid, these annular fibres 
have the power of grasping it by their contractions. 
Mucous follicles which empty their secretion by conspi- 
cuous excretive orifices are abundant at this part. The 
lining membrane of the nasal passage having reached 
the vomer, assumes a peculiar texture ; becoming thin, 
smooth, very dry, of a black colour, and apparently 
destitute of nerves and vessels. The two osseous 
nasal canals are closed at the superior or external ori- 
fice by a fleshy valve in the form of two semicircles, 
attached to the anterior margin of that opening, which 
it closes by means of a very strong muscle lodged above 
the intermaxillary bones. Inorderto open itsomeforeign 
body must press against it from below. When this 
valve is closed, it cuts oft’ all commimication between 
the nasal passages and the cavities above them. These 
cavities consist of two large membranous pouches 
formed by a dark-coloured mucous skin, which is much 
wrinkled when they are empty; but assuming, when 
distended, an oval figure, which in the porpoise equals 
the size of a common wine-glass. These two pouches 
are lodged beneath the integuments, in front of the 
nostrils; they communicate with an intermediate space 
immediately above the nostrils, the latter opening 
externally by a transverse semilunar slip. Very strong 
muscular fibres form an expansion, which closes in the 
upper surface of this apparatus; these fibres radiate 
from the whole circumference of the cranium to unite 
above the two pouches, being adapted to compress 
them forcibly. Let us suppose the Cetacean has 
taken into its mouth some water which it wishes to 
eject; it moves the tongue and jaws as if about to 
swallow it; but closing the pharynx, tire water is forced 
up into the nasal passages, where its progress is acce- 
lerated by annular fibres, until it raises the valve and 
distends the membranous pouches above. Once in 
these sacs, the water can be retained there until the 
animal wishes to spout. For that purpose, it closes the 
valve to prevent the descent of the water into the nasal 
passages, and it forcibly compresses the sacs by means 
of the muscular expansions which cover them ; and the 
fluid, thus compelled to escape by the narrow crescentic 
aperture, is' projected to a height corresponding to the 
force of the pressure.” Intimately connected with 
respiration — or rather, we should sa}', with the power 
of remaining under water for a considerable length of 
time without respiring — we find a special reservoir for 
arterialized blood; not formed however, by anyimusual 
enlargement of the arterial trunks, but by a remarkable 
extension of certain small arteries which are tivisted upon 
